ǂThe ǂeffect of Pb(II), Cd(II) and Pd(II) ions on the conformational changes of ovalbumin

[N. Mijin]

115 str.

Hemija/ Chemistry

Proteinske strukture su prirodno dinamičke i fleksibilne. Ova univerzalna karakteristika je apsolutno neophodna za biološku funkciju i relativnu stabilnost nativnih proteina. U bilo kom trenutku, proteini zauzimaju odgovarajuću strukturu, odnosno konformaciju. Promene u ovoj strukturi su krajnje odreĎene od strane faktora sredine u kojoj se dati proteini nalaze. Ove promene mogu biti minorne i funkcionalno neophodne, dok neke promene mogu biti drastične, krajnje izazivajući gubitak nativne strukture i prirodne funkcije polipeptida. Iako je gubitak nativne konformacije proteina u većini bioloških slučajeva nepogodan, sami konformacioni prelazi u termodinamički stabilniju formu predstavljaju potpuno prirodnu pojavu i osnovu za mnoge biohemijske procese. Glavni cilj ove disertacije je dalje rasvetljenje uticaja faktora koji utiču na konformacione prelaze proteina, konkretno dejstva jona teških metala i organometalnih kompleksa primenom ovalbumina kao model sistema. Radi ostvarenja ovog cilja, izvedena je strukturna analiza ovalbumina primenom izvesnih metoda poput FTIR spektroskopije za praćenje promena sekundarnih struktura, uključujući DLS i AFM metode za analizu dimenzija i morfologije novonastalih struktura. Spektrofluorimetrijske probe su primenjene za analizu hidrofobnosti ovalbumina, kao i za praćenje formiranja amiloidnih struktura. Rezultati analize su pokazali da je stepen formiranja amiloidnih fibrila srazmeran sa koncentracijom prisutnih jona teških metala, čije nespecifične interakcije su različito uticale na krajnju morfologiju fibrila. Dobijeni rezultati strukturne analize su takoĎe pokazali da ovalbumin predstavlja adekvatan model sistem za predviĎanje dejstva univerzalnih protein-ligand interakcija sa potencijalno novim hemoterapeuticima na bazi metala.

Protein structures are dynamic and flexible by nature. This universal characteristic is absolutely necessary for the proper biological function and relative stability of native proteins. Proteins, at any given moment, assume a certain structure, i.e. conformation. Changes in this structure are ultimately determined by the environmental factors by which a protein is affected. The changes induced by these factors may be minor, but functionally mandatory, while others might be drastic and ultimately result in the loss of the native fold and biological function of a polipeptide. Even though the loss of a protein’s native conformation is generally viewed as a negative scenario, conformational changes towards more thermodynamically stable forms represent entirely natural phenomena and the basis for many biochemical processes. The main goal of this dissertation is to further elucidate the effects of these factors on protein conformational changes, specifically the effects of heavy metal ions and organometallic complexes on ovalbumin as a model system. To this end, methods such as FTIR spectroscopy were used for secondary structure analysis, including DLS and AFM techniques for determining the protein's dimensions and morphology. Spectrofluorimetric dyes were also used to monitor protein hydrophobicity and amyloid formation. The obtained results show that amyloid formation is directly proportional to the concentration of present heavy metal ions, the non-specific binding of which had differing effects on the fibrils’ morphologies. Structural analyses results also showed that ovalbumin shows great promise as an adequate model system for the prediction of universal protein-ligand interactions with metal-based chemotherapeutic agents., Protein structures are dynamic and flexible by nature. This universal characteristic is absolutely necessary for the proper biological function and relative stability of native proteins. Proteins, at any given moment, assume a certain structure, i.e. conformation. Changes in this structure are ultimately determined by the environmental factors by which a protein is affected. The changes induced by these factors may be minor, but functionally mandatory, while others might be drastic and ultimately result in the loss of the native fold and biological function of a polipeptide. Even though the loss of a protein’s native conformation is generally viewed as a negative scenario, conformational changes towards more thermodynamically stable forms represent entirely natural phenomena and the basis for many biochemical processes. The main goal of this dissertation is to further elucidate the effects of these factors on protein conformational changes, specifically the effects of heavy metal ions and organometallic complexes on ovalbumin as a model system. To this end, methods such as FTIR spectroscopy were used for secondary structure analysis, including DLS and AFM techniques for determining the protein's dimensions and morphology. Spectrofluorimetric dyes were also used to monitor protein hydrophobicity and amyloid formation. The obtained results show that amyloid formation is directly proportional to the concentration of present heavy metal ions, the non-specific binding of which had differing effects on the fibrils’ morphologies. Structural analyses results also showed that ovalbumin shows great promise as an adequate model system for the prediction of universal protein-ligand interactions with metal-based chemotherapeutic agents.

agregiranje, amiloidni fibrili, ovalbumin, teški metali, mikroskopija atomskih sila, FTIR spektroskopija, efekat DMSO, hidrofobnost liganada, dinamičko rasejavanje svetlosti

aggregation, amyloid fibrils, ovalbumin, heavy metals, atomic force microscopy, FTIR spectroscopy, DMSO effect, ligand hydrophobicity, dynamic light scatterin

544.77.052.2:547.964.4(043.3)

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